First, he lacks the legal authority to do this. Decisions on delivery schedule are the purview of Congress, and every year for the past 30 years, America's elected representatives have mandated six-day delivery — a requirement remaining in force today.

Mr. Donahoe isn't above the law. Further, his attempted power grab flouts the political will of Congress; as recently as the last session, which ended in January, a bipartisan majority of representatives co-sponsored measures backing continuation of Saturday delivery.

It's not surprising that many lawmakers have questioned Mr. Donahoe's legal overreach, or that his explanations are so evasive.

On the merits, it's a disastrous idea. The postmaster general proposes trading 17% of service for 2% in savings — an irrational business plan. Indeed, when the USPS asked the agency's overseer, the Postal Regulatory Commission, in 2011 to support ending six-day delivery, this illogic was one of the factors cited by the commission in declining to endorse the plan.

So, too, was the finding that the savings were wildly inflated. The commission also noted that ending Saturday delivery would disproportionately affect the elderly, rural communities and small businesses. Those small businesses create more than two-thirds of all jobs in this country, and forcing them to hire expensive private contractors on weekends would impose new costs.

So ending Saturday delivery would jeopardize the USPS' future by sacrificing its competitive advantage, hurt tens of millions of Americans — and it wouldn't even solve the agency's financial woes.

That's because most of the red ink has nothing to do with postal operations. Rather, 80% of the red ink stems directly from the 2006 congressional mandate that the Postal Service do something no other agency or company is required to do: pre-fund future retiree health benefits. That mandate accounted for $11.1 billion in red ink in fiscal 2012 alone.

The postmaster general should address that problem, rather than seeking to override his authority by eviscerating a network that provides residents and businesses with the world's most efficient and affordable delivery service while uniting this vast country.

Fredric Rolando is the president of the National Association of Letter Carriers.

* This opposing view has been updated to reflect the print version of the Feb. 15 edition.